In a conventional laparoscopic or endoscopic operation, an instrument with a rigid or flexible shaft is inserted into the body through a cannula or working channel of a flexible endoscope. Upon locating a target tissue, a particular surgical effector is deployed through the instrument's lumen, the end effector being visualized by an operator on a video screen. Generally, such instruments are built with a single lumen shaft capable of housing only one such effector. There are, however, several exceptions: certain operations require that several functions are performed in close proximity of time. For such cases, when there is not enough time to allow for the insertion and subsequent withdrawal of multiple instruments, multi-lumen instruments have been devised. In multi-lumen instruments, each lumen houses a different surgical effector, all effectors being part of the same surgical instrument assembly.
U.S. Pat. No. 5,759,187 to Nakao et al, describes such a device for polyp resection and subsequent retrieval. Pursuant to the disclosure of the '187 patent, snare cauterization and retrieval operations are performed with a single surgical instrument assembly comprising a tubular sheath longitudinally divided into two lumens by a septum. One lumen houses a cauterization loop connected to a metal push wire, the wire being slidably disposed in one of the lumens. The second lumen houses an auxiliary loop with flexible web member slidably attached, the web member forming a capture pocket. The loop with capture pocket is operably connected to a second push wire slidably disposed inside the second lumen. A bifurcated handle is operably connected respectively to the cauterization loop and the auxiliary loop with capture pocket. When an arm of the bifurcated handle is actuated, its respective end effector is ejected. The handle of the dual lumen device described in the U.S. Pat. No. 5,759,187 is Y shaped. This Y shaped handle is ubiquitous to other double lumen devices, e.g. devices used for endoscopic retrograde cholangio-pancreatography and devices used for cardiac catheterization and subsequent angioplasty procedures. This handle consists of a lure that extends about the base trunk section, with rigid arms that project from the base of the Y securely linked together.
A similar design is disclosed in U.S. Pat. No. 7,957,417 to Nakao et al, disclosing an instrument solution for removal of common bile duct stones through the Ampulla of Vater. FIG. 37A of the '417 patent demonstrates a triple lumen device with corresponding three pronged handle, each lumen being designated to house an effector with different function.
A cautery retrieval polypectomy snare device with a Y handle described in U.S. Pat. No. 5,759,187 was manufactured and marketed, but had to be withdrawn from use because of several problems that this handle presented. The actuating arm of the snare with retrieval pouch malfunctioned on numerous occasions because the Y configuration of the two actuators: the respective push-rods of the Y handle, as connected to their respective push wires and end effector, were unstable and flimsy due to the angle created by the Y connector. This caused the push rods to buckle or brake off altogether. The problem was exacerbated when the device was used in conjunction with a flexible colonoscope inside a patient's colon. The colonoscope is long and especially tortuous when inserted deeply into the normally convoluted colon. Actuating a bifurcated handle to effect ejection of the retrieval pouch for example, required application of substantial force to that arm of the Y handle, causing buckling of the actuating push rod of the handle. As a result, the retrieval basket could not be consistently ejected from the instrument's double lumen catheter when the colonoscope was deep inside a patient's colon.
Another problem that the Y shaped handles presented was its cumbersome and ergonomically difficult operation for the endoscopist whose hands were occupied wielding the endoscope. Furthermore, such a handle was difficult to package, requiring special packaging designs to support the fragile Y shaped structure. The large size of the package required for the Y shaped handle took up extra shelf space in the operating room, proved costly to sterilize, store, and ship. Furthermore, manufacturing a bifurcated handle increased the price of the instrument, resulting in an ultimate increase in price to the patient.
U.S. application Ser. No. 12/287,717 to Nakao filed Oct. 10, 2008, describes a novel handle for a double-lumen cautery retrieval snare assembly used to cut and retrieve polyps or other lesions in the gastrointestinal tract. This instrument utilizes an electrically conductive cauterization loop end effector, and a flexible auxiliary loop end effector with a flexible web member connected to the loop as described above. The surgical instrument assembly further comprises a tubular sheath or catheter that is longitudinally divided into two lumens. One of the two lumens houses the electrically conductive loop connected to an actuation cable slidably disposed within the lumen. The second contains an auxiliary loop with capture pocket, connected to its own designated cable, slidably disposed inside the second lumen. So far this duplicates the invention taught in U.S. Pat. No. 5,759,187 to Nakao et al. The difference lays in the invention of the handle. The handle disclosed in the patent application Ser. No. 12/287,717 is not bifurcated, but is configured with a single stemmed body, shaped and sized almost identically to handles used in single lumen endoscopic devices. Yet, the handle allows for separate actuations of two different end effectors.
The handle of U.S. application Ser. No. 12/287,717 includes a plurality of actuators disposed in a common plane. The actuators lay adjacent to one another within a single spine handle body. One actuator comprises a thumb ring affixed to a proximal end of the handle body, and a pair of finger rings affixed relative to one another and longitudinally slidable along the handle body. The pair of finger rings is designed to actuate one of the end effectors. A second actuator knob is longitudinally slidable along a handle slot in the handle body, operably connected to the second end effector. The handle assembly contains at least two push rods that lay parallel to one another, one push rod connected to one of the actuators and to a respective push wire slidably disposed within its respective sheath lumen, the cable in turn being connected to a respective end effector. The other push rod is connected to the other actuator and, through its connection to the intervening push wire, is operably connected to a second end effector.
When a prototype of the invention disclosed in U.S. application Ser. No. 12/287,717 was built, this inventor found certain shortcomings in the design. In particular, the actuator knob connection to its respective push rod was too flimsy to function in a consistent manner. The limited real-estate available inside the handle spine precluded a thicker, and thus a more sturdy connection between actuation knob and push wire. Actuation was especially problematic when the instrument assembly was inserted into a biopsy channel of a tortuous flexible colonoscope. Under those conditions, the increased force required to eject the respective end effectors caused the push rods in the handle to buckle under the tension.